Multi-stable fluid device



April 7, 1964 Filed Dec. 20, 1961 R. E. NORWOOD MULTI-STABLE FLUID DEVICE INDICATOR SECOND STACE SUCTION FIG. 1

2 Sheets-Sheet 1 FIG.3

IN VE N TOR ATTORNEY April 7 1964 R. E. NORWOOD 3,128,039

MULTI-STABLE FLUID DEVICE POWER STREAM FLOW THROUGH EACH SWITCHING ELEMENT United States Patent 3,128,639 MULTl-STABLE FLUiD DEVitlE Richard E. Norwood, Endicott, N.Y., assigncr to International Business Machines Corporation, New York, N.Y., a corporation of New York Filed Dec. 20, $61,812:. No. 16%,779

9 Claims. (Ql. 235--61) This invention relates to multi-stable fluid devices, and more particularly to multi-stable devices embodying at least one pair of bistable'and monostable fluid switching elements coupled to provide a fluid flip-flop device and capable of being cascaded to form a multi-stage binary counter.

Recently, considerable effort has been directed toward developing fluid devices capable of switching a fluid power stream to one of a plurality of stable states without the use of moving parts. These devices may be of the type referred to as fluid amplifiers, so called because the switching of the device can be accomplished by a control stream of lesser energy than the power stream. This control stream may be maintained continuously as long as it is desired to keep the power stream diverted to a selected outlet. However, if the device is designed to embody the feature known in the art as boundary layer lockon, the control stream need not be continuous but may be a short pressure fluid pulse merely of suflicient duration to effect diversion of the power stream and initiate lock-on.

It has been suggested that this .boundary layer lockon" may be effected by setting back the outer or remote part of a particular divergent outlet at the downstream end of a throat or nozzle through which the fluid flows from the inlet to the outlets. With arrangements of this type, when the fluid stream is diverted to the particular outlet, a low pressure region is created at the downstream end of the throat and adjacent the outer part of the outlet wall. Thus, a self-regenerating suction is created and maintained in this region. This suction tends to maintain the power stream diverted to the particular outlet even after the fluid control pulse is terminated and until the power stream is rediverted to another outlet.

With this arrangement, critical design relationships must be followed in order to produce the desired effect. However, even where such design criteria are followed, an adverse or unanticipated pressure gradient can cause undesired switching of the device. Thus, this self-regenerating lock-on is not reliably achieved over a wide range of operating conditions that are or may be encountered in use of the device. For example, the kinetic energy of the power stream may vary somewhat due to pressure surges from the source, or due to variations in back pres sure from any restrictions or loads against which the fluid stream may be directed upon leaving a particular outlet; and these variations could produce an adverse pressure gradient sufficient to cause undesired switching of the device.

If devices of this general type can be made to operate reliably in response to fluid pulses of short duration, such devices may be arranged in cascade to provide a reliable fluid binary counter for counting successive fluid pulses received from a source.

Accordingly, one object of this invention is to provide an improved fluid device of improved stability which will remain reliably diverted to a selected outlet after an input pulse dies, despite any reasonably foreseeable condition which might tend to create an adverse pressure gradient.

Another object is to provide a pair of fluid switching elements coupled to provide a regenerative feedback, whereby an output will be obtained from a particular ICC outlet of one of the elements upon every other successive pulse of short duration from a single source.

Another object is to provide fluid switching elements capable of being combined in cascade to provide a fluid binary counter.

Still another object is to provide a reliable fluid binary counter.

According to these objects, a fluid device embodying the invention comprises a monostable element providing first and second control ports selectively chargeable with pressure fluid pulses for diverting one fluid power stream to a first or second outlet, respectively; and a bistable element providing third and fourth control ports selectively chargeable with pressure fluid pulses for diverting another fluid power stream to a third or fourth outlet, respectively. One conduit conveys pressure fluid from the second outlet to the third control port. Another conduit conveys pressure fluid from the third outlet to the first control port. Each element has a reset port concurrently chargeable with a pressure fluid pulse to set the deviceto a normal condition in which the respective streams exit through the first and third outlets, and fluid is thus supplied to said other conduit. Input pressure fluid pulses are supplied concurrently to the second and fourth control ports.

Thus, upon the first input pulse following reset, the one stream in the monostable element will not switch because of the bias pressure fluid in the other conduit, but the stream in the bistable element will switch to the fourth outlet and thus terminate such bias. Upon the next pulse, the one stream in the monostable element will switch to the second outlet, causing pressure fluid to flow via said one conduit and thus switch said other stream to said third outlet; and this, in turn, will supply pressure fluid to the other conduit and cause the stream in the monostable element to be diverted back into the first outlet.

Hence, upon successive input pulses to second and fourth control ports, the stream through the bistable element will be switched as necessary to provide continuous outputs alternately in the fourth and third outlets; but the stream through the monostable element will remain diverted to the first outlet except momentarily upon every other pulse during which it will deliver a regenerative feedback pulse to flip the device to its normal state or condition. Consequently, the device, as thus far described, is in effect a fluid flip-flop device.

Pairs of these monstable and bistable elements may be cascaded to form a multistage fluid binary counter. All that is necessary is to connect the second and fourth con trol ports of the first stage to a source of input pulses; but connect a branch of the one conduit of one stage to the second and fourth control ports of the next stage. Thus, the regenerative feedback pulse delivers periodically to the one conduit will serve also as a carry pulse to the next stage.

These fluid devices will, of course, operate in the manner described only if the fluid power streams willremain switched after the input and the regenerative (or carry) pulses die, because such pulses are of short duration. To assure lock-on of the streams to a desired outlet, suction ports are pnovided in the outer wall of each outlet to hold a stream locked against said Wall despite an adverse pressure gradient. Also, the throat through which the power stream is directed en route from the inlet to the outlets is of such configuration as to provide a velocity profile which enhances lock-on.

The reset ports desirably permit switching of the streams as necessary to reset the counter to zero (or reset a flipflop device to a normal condition) without requiring shutoff of the power stream.

The foregoing and other objects, features and advan- 3 tages of the invention will be apparent from the following more particular description of a preferred embodiment of the invention, as illustrated in the accompanying drawings, wherein:

FIG. 1 is a schematic view of a multistage fluid binary counter em bodying a plurality of fluid switching element-s constructed and interconnected in accordance with the invention;

FIG. 2 is a timing diagram showing the states of the various switching elements of the counter as suowssive pulses are delivered from a pulse source;

FIG. 3 is an elevation-a1 section view of a typical switching element of the counter; and

FIG. 4 is a section taken along the line 4-4 of FIG. 3.

DESCRIPTION As shown in FIG. 1, the fluid binary counter embodying the invention comprises a plurality of fluid switching elements, such as 10, 11, 12, 13. These elements are arranged in pairs, such that elements 11) and 11 constitute the first stage of the counter, and elements 12 and 13 constitute the second stage thereof. Additional pairs of elements (not shown) can be arranged in like manner to constitute subsequent stages of the counter.

As shown in FIGS. 3 and 4, switching element (and also each ot the other switching elements) comprises an inlet chamber 14 defined pant by side walls 15a, 15!) that curve converging to (form a throat 13. These walls are curved convexly to produce a velocity profile as indicated at 17 (FIG. 3).

Upon reaching the throat 16, the walls 15a, 15!) start to diverge without any setback and in straight lines that depart from said walls without interruption and at substantially equal angles from an imaginary plane X passing coaxially through the throat. These straight lines define the outermost or remote walls 18a, 18b of respective outlets 19a, 1%. As illustrated, these outlets are separated by a V-shaped wedge-like isolator 2% having an apex that preferably lies in plane X; however, it is not essential that a flow-splitting wedge-like isolator be used, nor is it essential that the inner walls of outlets 19a, 1% be substantially parallel to the outer walls 13a, 18b as shown in the draw ings.

Open to the downstream end of throat 16 are oppositely arranged control ports 21a, 21b. Downstream of these control ports are oppositely arranged suction ports 22a, 2212 that open through the outer walls 18a, 15b, respectively. Between the ports 21b and 22b is a reset port 23 that opens through wall 1815.

As shown in FIG. 1, a suitable source, such as a pump 25 is adapted to continuously supply fluid at a preselected pressure to a supply pipe 26 having branches lea-ding to the inlet chamber 14 of each fluid switching element of the counter. Also, a suitable source of vacuum, such as a vacuum pump 27, is adapted to continuously apply suet-ion concurrently to both suction ports 22a, 22b of each switching element via branches of a suction pipe The reset port 23 of each switching element is connected via branches or a reset pipe 29 to a source 36 of reset pressure fluid pulses.

The control ports 21a of elements 19, 11 of the first stage of the counter are connected via branches of a pipe 31 to a source 32 of input pulses. However, the control ports 21b of elements 10, 12 are connected to pipes 33, 33, respectively, each having a mouth which is preferably open to the exit end of the outlet 19a of the corresponding element 11 or 13, respectively. On the other hand, control ports 21]) 0t elements 11, 13 are connected to pipes 34, 34, respectively. Pipe 34 has one branch that leads to the exit end of, but is not sealingly connected to, the outlet 1% of element 10; and other branches ct said pipe are connected to control ports 21a of the elements 12, 13 for the succeeding stage to provide a carry pulse to said stage. Similarly, pipe 34- has a branch that leads to the exit end of, but is not sealingly connected to, outlet 19b of element 12; and other branches of said pipe are connected to the control ports 21a (not shown) for the elements (not shown) of the next stage to provide a carry pulse to the third stage. The mouths of the pipes 33, 33', 34, 34 are preferably of smaller diameter than the width of the associated outlets 1% or 1% so that only a part of the energy of the power stream will be channeled into such pipe for control purposes. In other words, a significant part of the energy of the power stream passes to atmosphere (or to a sump) around the last-mentioned pipes. This is because the energy of the fluid in the power stream may be many times higher than the energy of fluid which is necessary or desirable in the control ports.

Outlet 1% of elements 14 12 are open to atmosphere (or to a sump if the fluid is liquid, rather than gaseous). However, outlets 1% of elements 11, 13 are connected to suitable fluid pressure actuated utilization devices, illustrated as indicator devices 35, 35', respectively. These 35, 35 may be in the form of vanes (not shown) which are biased to an ineffective or lowered position and are driven upward to a visible position by and so long as a stream of fluid under pressure is directed thereagainst. Of course, the utilization device may take some other form, and need not be an indicator.

For purposes of illustration, the sources 30, 32 may be assumed to be solenoids which respond to momentary energization (or de-energization) of an electromagnet (not shown) to momentarily supply fluid under pressure to the corresponding pipe 29 or 31, respectively, and thus provide, in effect, a fluid pressure pulse therein.

OPERATION Assume initially that vacuum pump 27 is applying suction via pipe 28 to both outlets 19a, 19b of each switching element 10, 11, 12, 13; and that pump 25 is supplying a continuous stream of fluid under pressure to the inlet chamber 14- of each of said elements. Under these conditions, a fluid power stream will be flowing continuously from the respective inlet chamber 14 through one or the other of the outlets 19a, 19b of each of the switching elements.

Reset pulse.-Assume now that at time T (FIG. 2) a reset pulse is delivered from reset source 30 via pipe 29 to the reset port 23 of each switching element. Each reset pulse will impinge upon, and positively divert, the fluid power stream in that particular switching element to outlet 1% of such element. Thus, each indicator device 35, 35' and also an indicator 35 (see FIG. 2) for the third stage will assume its ineflective or lowered position, thereby resetting the counter to zero and giving a binary indication of 000 (FIG. 2).

A more detailed explanation of how the fluid power stream is switched and eflectively locked-on to a particular outlet responsively to reset pulses or input pulses will be given after the explanation of the operation of the counter is completed.

With the counter reset to zero, the fluid power streams will exit from outlet 19a of each switching element 10 to 13. Thus, as viewed in FIG. 1, some of the fluid leaving outlet 19a of the rightmost element, such as 11, 13, of each stage of the counter will flow via the corresponding pipe 33, or 33 to the control port 21b of the leftmost element, such as 10, 12, of that same stage.

First input pulse-When an input pulse is delivered from source 32 to pipe 3-1 at time T '(FIG. 2), the fluid under pressure which has been flowing continuously via pipe 33 to element 19 of the first stage will positively hold the stream diverted to outlet 19a of said element despite the pulse delivered to control port 21a of that element. However, the pulse concurrently delivered via a branch of pipe 31 to control port 21a of element 11 will shift or divert the fluid power stream from outlet 19a to outlet 1912 of said element. Some of the diverted pressure fluid will thus actuate the indicator 35 to denote that one input pulse has been received.

d e3 Meanwhile, as soon as the power stream in element 11 is diverted from outlet 419a to outlet 1%, the supply of pressure fluid to pipe 33 will be cut oh. This will permit the stream in element .10 to shift when the next input pulse is delivered to pipe 31. Also, since no switching occurred in element 14?, no pressure fluid will be supplied to pipe 34. Hence, no signal will be delivered to the elements 12 and 13 of the second stage;and there will therefore be no switching of the fluid streams in these elements. Accordingly, the indicators 35, 35', 35" will give a binary indication of -1 (see FIG. 2).

Second input pulse.When the second input pulse is delivered from source 32 to pipe 31 at time T (FIG. 2), no immediate change will be effected in the course of the power stream in element 11 because it is already diverted to outlet 1%. However, since no pressure fluid is now being supplied to pipe 33, the second pulse will divert the power stream in element to outlet 1%, thus supplying some pressure fluid to pipe 34.

Some of the pressure fluid supplied to pipe 34 will flow through control port Zlb of element 11 and shift its power stream from outlet 1% to outlet 1%; this, in turn, will cause pressure fluid to be supplied via pipe 33 to control port 21b of element 10 for switching its power stream to outlet 19a and thus cutting oil" the supply of pressure fluid to pipe 34.

Meanwhile, some of the pressure fluid supplied to pipe 3-4 will flow to control ports 21a of the elements 12 and 13 of the second stage. The operation will then be identical with that described for elements MD and 11 of the first stage upon delivery of the first input pulse. In other words, there will be no change in the course of the fluid stream through element 12 because of the pressure fluid being supplied through pipe 33. However, the power stream through element 13 will be diverted to outlet 1% for actuating indicator 35.

Thus, the second pulse will cause indicator 35 to resume its ineffective or lowered position, but will actuate indicator 35 to its visible position. Indicator 35 will not he visible because no pulse has thus far been delivered to the third stage. Accordingly, the indicators will give a binary indication of 010 corresponding to two pulses.

Third input pulse.Just before the third input pulse is delivered to pipe 31 at time T (FIG. 2), the power streams for elements 10, ill will be flowing through outlets 19a thereof. Thus, when the third pulse is delivered, the stream of element 10 will not be switched; however, the stream of element 11 will be switched to output 191) and thus actuate indicator 35, in exactly the same manner as described in connection with the first input pulse. No pulse will be delivered to pipe 34-. Hence, the streams of elements 12, 13 will not be switched, and supply of pressure fluid to indicator 35 will thus be maintained. Accordingly, indicator 35 will remain inactive, and indicators 35', 35' will be held up concurrently to provide a binary indication of 010 denoting that the third pulse has been received.

Fourth input pulse.-When the fourth pulse is delivered to pipe 31 at time T (FIG. 2), the power stream flowing through element It) will be switched to outlet 1% and set up a chain reaction whereby the pressure fluid supplied to pipe 3 will effectively switch the stream through element 11 to outlet 1% and pipe 33. This, in turn, will switch the stream through elei 161111 It) to outlet 19a and terminate supply of pressure fluid to the carry pipe 34. Thus, indicator 35 will drop to its ineifcctive position.

Meanwhile, some of the pressure fluid supplied to the carry pipe 34 will flow to ports 21a of element 12, 13. Since the stream through element 13 is then flowing through outlet 1%, the pulse will have no immediate direct effect on the stream in said element. However, the companion pulse concurrently delivered to element 12 will effect switching of its power stream to outlet 1% for thereby supplying pressure fluid to carry pipe 34'. This will switch the stream through element 13 to outlet 19a and pipe 33, to drop indicator 35 and switch the stream through element 12 to outlet 19a to terminate the carry pulse.

Meanwhile, the carry pulse which had been delivered to carry pipe 34' will switch an element Z (FIG. 2) of the third stage to actuate the indicator 35", while a complementary element Y will remain unaffected. These elements Y and Z correspond to elements 10, 11, respectively; and switching of the respective fluid streams thereof is controlled in the same manner as already explained for the elements 10, 11. The only difference is, of course, that pulses will be delivered less frequently to the control ports 21a of each succeeding stage. This is because pres sure fluid is supplied to pipe 31 and hence to the control ports 21a of the first-stage elements 10, 11 during every pulse from source J2. However, pressure fluid is supplied to pipe 34 only upon every other pulse from source 32, and pressure fluid is supplied to pipe 34' only upon every fourth pulse from source 32.

Thus, the fluid power streams through elements 10, 11, 12, 13, Y and Z (and any additional elements which may be added for subsequent stages) will be switched, in the manner and with a binary relatedfrequency above described, during and as a result of the first four pulses from source 32. During the next four pulses, the streams from these elements will be switched in the manner which is shown schematically in FIG. 2 to demonstrate the operating principle of the counter for a third stage and any additional stages which may be desired.

Switching element configuration.-Obviously, the counter will operate in the manner above described only if boundary layer lock-on control can be reliably achieved. This is because switching of the power streams is eliected by fluid pulses of short duration delivered to control ports 21a, 21!), or the reset ports 23.

Accordingly, to achieve reliable lock-on, each switching element of the counter is preferably constructed as shown in FIGS. 3 and 4. It will be noted that the walls 15a, 151) are convexly curved and converge toward the throat 16 to give a velocity profile (indicated at 17 in FIG. 3) that assures a high degree of fluid entrainment. This configuration assures that when the particular outlet 19a or 1912 is conducting, the volume of fluid and its velocity will be greatest adjacent the divergent outer wall 18a or 18b of the then conducting outlet. This provides a low pressure region along the wall 18:: or 18b of the then conducting outlet which, in turn, helps to assure that the stream will remain locked-on by boundary layer control to that particular outlet once it is diverted thereto. However, since this self-regenerating lock-on can be destroyed by an adverse pressure gradient, the suction ports 22a, 22b are provided to enhance the attraction of the stream to the outer Wall of the conducting outlet and prevent undesired switching of the stream in event of an extraneously created adverse pressure gradient.

Accordingly, it will be understood that a reset pulse from source 30 or a pulse to either of the control ports 21a or 21b need merely be of suflicient temporary duration and magnitude to overcome the cumulative holding or biasing effect of the suction applied through the appropriate suction port 22a or 22b and the self-regenerating lock-on provided by the improved velocity profile 17. Thus, once the streams are diverted to particular outlets 19a or 19!), these streams will remain so diverted due to the combined effect of the suction from the appropriate suction port and the self-regenerating lock-on.

The configuration of each switching element is purely symmetrical except for the provision of the reset port 23. Consequently, the power stream will not be inherently biased or directed toward a particular outlet.

By merely delivering a short reset pulse to each reset port 23, the switching element (or an entire counter composed of a plurality of such elements) may be reset to zero without requiring a shutoli of the power stream being supplied by the pump 25 to each such element. This not only saves time but it also eliminates an undesirable and unnecessary cause of pressure surges and rarefaction waves in the power streams.

As illustrated, the pipes 33, 33', 34, 34', and the pipes leading to indicators 35, 35' are shown with their mouths substantially coaxially aligned with the appropriate outlets 19:: or 1%. This is because, in the embodiment illustrated, it was desired to recover only a small proportion of the energy available from the power stream. To effect greater degrees of recovery of energy, the mouths of these pipes should be disposed more in line with the outer Walls 18a or 18b of the respective elements. In this connection, it is to be noted that the proportion of energy recoverable is enhanced by use of the suction ports 22a, 22b because the latter provide more reliable lock-n of the power stream to the walls 18a and 18b, respectively, and eliminate undesirable energy-dissipating eddy-currents.

While the invention has been particularly shown and described with reference to a preferred embodiment thereof, it will be understood by those skilled in the art that changes in form and details may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

1. A fluid device comprising first and second switching elements each adapted concurrently to convey a respective fluid power stream from an inlet to a selectable one of a plurality of outlets, and a plurality of control ports arranged to direct pressure fluid jet pulses laterally against each stream to switch it to a desired outlet; means for providing fluid feedback connections between at least one outlet of each element and at least one control port of the other element; and means for delivering pressure fluid pulses concurrently to other control ports of each element to switch the streams as necessary to selectively connect the stream in said second element to different outlets in succession responsively to successive pulses and connect the stream in said first element to the other outlet thereof except temporarily during every other such pulse.

2. A multi-stable fluid device responsive to discrete fluid pressure pulses from a source, said device comprising two elements each including means for conveying a respective fluid power stream to any of a plurality of outlets and each including means including control ports selectably chargeable with pressure fluid pulses to switch the corresponding stream to a desired one of the outlets of such element; a vacuum source for applying suction continuously to the remote part of the wall of each outlet to create a low pressure region near the corresponding control port to aid boundary layer lock-on of the appropriate stream to that outlet to which it is diverted by a pressure pulse; conduit means fluid-pressure-connecting at least one of the outlets of each element with a control port of the other element; means connecting other control ports of each element to the source, whereby upon each successive pulse from the source the stream in one of the elements will be switched to different outlets in succession to provide continuous stable outputs therein; and reset means for each element for switching its stream to one preselected outlet, said reset means including a reset port opening through the remote part of the wall of a preselected different outlet, and means for supplying a pressure fluid pulse of limited duration to the reset port to effect such switching.

3. A fluid device comprising two elements each comprising means for receiving a fluid power stream, and providing two control ports and two outlets; one conduit connecting one outlet of one of the elements With a control port of the other element; another conduit connecting an outlet of the other element with a control port of said one element; and means for conveying discrete fluid pulses to the respective other control ports of said elements concurrently to cause every other pulse to divert the stream in said other element to the other outlet thereof and away from said other conduit while the one stream in said one element flows Without diversion through the other outlet thereof, and upon each intervening pulse cause said one stream to successively switch to said one conduit and by diverting the other stream to said other conduit thereby divert said one stream from said one conduit to said other outlet of said one element as soon as said intervening pulse ends.

4. A fluid device comprising two elements, each comprising means providing an inlet for conveying a fluid power stream, a plurality of outlets, and a plurality of control ports selectively chargeable with pressure fluid for switching the stream in that element to desired outlets; means for supplying input pressure fluid pulses concurrently to at least one control port of each element; and means interconnecting one outlet of each element with one other control port of the other element as necessary to cause successive input pulses to switch the stream in a certain one of said elements alternately back and then forth between two outlets thereof and upon every other pulse switch the stream of the remaining element momentarily from one outlet thereof to the other outlet thereof for providing a regenerative signal pulse.

5. A bistable fluid device comprising means providing first and second control ports adjacent one fluid power stream and selectively chargeable with fluid under pressure for diverting said stream to a first outlet or a second outlet, respectively; means providing third and fourth control port adjacent another fluid power stream and selectively chargeable with fluid under pressure for diverting said other stream to a third or fourth outlet, respectively; conduit means connecting the second outlet with the third control port, and the third outlet with the first control port; and a source of fluid pressure pulses connected to the second and fourth control ports, whereby upon successive pulses from the source continuous fluid outputs will be obtained alternately in said third and fourth outlets, and a continuous output will be obtained from said first outlet except momentarily after a pulse switches said one stream to said second outlet and causes pressure fluid to be conveyed via said conduit means for successively switching said other stream to said third outlet and then said one stream to said first outlet.

6. A multi-stage fluid binary counter comprising a plurality of devices of the type defined in claim 5 arranged in cascade, such that the source supplies pulses directly only to the first stage, and the second outlet of each stage is connected to the second and fourth control ports for the following stage to provide carry pulses to the latter stages, and a utilization device for each stage actuated by and when pressure fluid is supplied to the fourth outlet of that stage.

7. A multi-stage fluid binary counter for counting a series of discrete fluid pulses from a source, each stage comprising first and second fluid switching elements, each element including means providing an inlet conveying a fluid power stream to a first or second outlet, and control ports open to the inlet for selectably conveying pressure fluid to switch the stream to a selected one of the outlets; means connecting the second outlet of the first element to one control port of the second element, means connecting the first outlet of the second element to one control port of the first element, means connecting respective other control ports of said elements to each other, and connecting the said other control ports of the first stage to the source, and means connecting the second outlet of the first element of each stage to said other control ports for the following stage, such that upon one pulse from the source one of the streams will be switched to the second outlet of the second element of the first stage, and upon the next pulse the other stream will be temporarily switched to the second outlet of the first element of the first stage to initiate one pulse for the next stage and also automatically effect switching of the second element of the first stage from its second to its first outlet and then as soon as said next pulse dies, cause switching of the first element from its second to its first outlet; and indicator means for each stage actuated by pressure fluid supplied to the second outlet of the second element of each stage to binarily count the pulses received from the source.

8. A cyclically operable fluid device comprising first and second elements, each having control ports for receiving pressure fluid pulses, an inlet for receiving a power stream, and a pair of outlets to which the stream may be alternately switched by such pulses; means for fluid coupling one outlet of each element to one control port of the other element; means operated responsively to discharge of pressure fluid from the other outlet of the second element to perform a desired control operation; and means for delivering input pulses concurrently to the respective other control port of each element, thereby to cause every other pulse to switch one of the streams to said other outlet of said second element and cause each intervening pulse to switch the other stream from one position to provide a temporary carry pulse that is transmitted via the coupling means and second element to reswitch said other stream back to said one position and terminate said carry pulse.

9. A device according to claim 8, wherein, upon successive input pulses, said one stream operates between two stable states during which such stream flows continuously through one or the other of the outlets of said second element, thereby to operate in the manner of a fluid flip-flop.

References Cited in the file of this patent UNITED STATES PATENTS 3,001,539 Hurvitz Sept. 26, 1961 3,001,698 Warren Sept. 26, 1961 3,024,805 Horton Mar. 13, 1962 FOREIGN PATENTS 1,278,781 France Nov. 6, 1961 OTHER REFERENCES Future for Fluid Amplifiers? Electronics magazine, page 41, March 25, 1960. 

4. A FLUID DEVICE COMPRISING TWO ELEMENTS, EACH COMPRISING MEANS PROVIDING AN INLET FOR CONVEYING A FLUID POWER STREAM, A PLURALITY OF OUTLETS, AND A PLURALITY OF CONTROL PORTS SELECTIVELY CHARGEABLE WITH PRESSURE FLUID FOR SWITCHING THE STREAM IN THAT ELEMENT TO DESIRED OUTLETS; MEANS FOR SUPPLYING INPUT PRESSURE FLUID PULSES CONCURRENTLY TO AT LEAST ONE CONTROL PORT OF EACH ELEMENT; AND MEANS INTERCONNECTING ONE OUTLET OF EACH ELEMENT WITH ONE OTHER CONTROL PORT OF THE OTHER ELEMENT AS NECESSARY TO CAUSE SUCCESSIVE INPUT PULSES TO SWITCH THE STREAM IN A CERTAIN ONE OF SAID ELEMENTS ALTERNATELY BACK AND THEN FORTH BETWEEN TWO OUTLETS THEREOF AND UPON EVERY OTHER PULSE SWITCH THE STREAM OF THE REMAINING ELEMENT MOMENTARILY FROM ONE OUTLET THEREOF TO THE OTHER OUTLET THEREOF FOR PROVIDING A REGENERATIVE SIGNAL PULSE. 